Question: What do the following two equations represent? $-5x+5y = -4$ $-15x-15y = 5$
Solution: Putting the first equation in $y = mx + b$ form gives: $-5x+5y = -4$ $5y = 5x-4$ $y = 1x - \dfrac{4}{5}$ Putting the second equation in $y = mx + b$ form gives: $-15x-15y = 5$ $-15y = 15x+5$ $y = -1x - \dfrac{1}{3}$ The slopes are negative inverses of each other, so the lines are perpendicular.